Most oil, gas, geothermal, and water supply wells produce formation solids along with the produced fluids. These formation solids, which are primarily fine sand, sometimes accumulate in the well bottom, often reducing fluid flow from the producing formation, and, often causing down-hole pumps to malfunction. These accumulations of sand must be removed from time to time if production operations are to continue in an economic manner. The general practice is to circulate the sand out of the well by means of a surface pump and the existing string of production tubing, which is progressively lowered as the sand is cleaned out. However, sometimes the sand is bound together by tar, iron oxide, lime, or some other substance, which makes it impossible to circulate the sand out of the well. In other situations the producing zone may be so depleted that it is impossible to circulate the sand out of the bottom of the well because of the low formation pressure in the producing zone which prevents the circulating fluid from returning to the surface.
When it is not possible to circulate the sand out of the well the general practice is to employ a wire-line bailer, or a wire-line sand pump to impact the sand and remove the loosened sand from the bottom of the well. However, this procedure requires a multidude of wire-line round trips to and from the bottom of the well, which is very time consuming. Therefore, if a down-hole sand pump were constructed that could impact the consolidated sand at the bottom of the well, and continuously pump the loosened sand, along with the cirulating fluid, to the surface, such a sand pump system would take considerably less time than the wire-line methods currently in use. If such a down-hole sand pump system were to force the circulating fluid and the sand up through a string of tubing, then there would be no pump pressure applied directly to the producing zone, and, therefore, such a pump system could perform its work regardless of the formation pressure.
A down-hole sand pump that is required to force sand-laden fluid to the surface, sometimes against a considerable pressure head, must be designed and constructed in such a manner so as to prevent the abrasive fluid from eroding components of the pump that are vulnerable to such abrasive fluid. Therefore, such a down-hole sand pump must be equipped with an adequate seal and wiper system so as to prevent fine sand from entering such a vulnerable component system, and such a down-hole sand pump must be equipped with a means to automatically adjust the seal and wiper system to compensate for wear of this component system.
Whereas the inside of the lightweight composite pipe would be protected from the abrasive sand-laden fluid by the Magnus effect created by the turbulently-flowing fluid which creates a two-phase transport core centered within the composite pipe, the outside of the composite pipe must be protected against abrasion from the steel casing or the formation wall, particularly, in high-angle directionally-drilled wells. Therefore, the outside of the lightweight composite pipe must be prevented from coming in contact with any surface that might damage the wall of the composite pipe, yet such a pipe-protector system must be designed and constructed in such a manner so that the pipe-protector system itself does not wear or otherwise damage the wall of the composite pipe.